This invention relates to apparatus for skimming liquid from the surface of a liquid body which includes two liquids of different densities.
The invention can be used to separate any mixture of liquids which separate under gravity, but it is especially useful in treating water covered by a layer of oil.
"Tramp" oils (hydraulic oils, lubricating oil for mills, lathes, and drill presses, transmission oil, and any other undesirable oil) are a source of many problems associated with wash water used in industrial parts washers, and with water-based coolants (which include a water-miscible organic lubricant) used in machining and grinding operations. The coolants are designed primarily to lubricate and cool the work and the cutting or grinding surfaces of the machine doing the work. The coolants reduce heat build-up during the machining or grinding process, and prevent the burning of parts, reduce distortion in the work piece, extend tool life, and permit faster production.
Machine coolants include oils, emulsifiers, and water-soluble oils to combine the lubrication property of cutting oils with the cooling ability and economy of water. The machine coolants are fairly expensive and, therefore, are recirculated for various machining operations. Wash water used in industrial parts washers is also recirculated to reduce costs. Coolants and wash water pick up various amounts of tramp oil during machining, grinding or washing operations.
Most coolant formulations absorb tramp oil if the two materials remain in intimate contact for a sufficient length of time. Absorbed tramp oil can change the desirable properties of the coolants, thereby negatively affecting tool life, surface finish of work pieces, and skin sensitivity of tool operators. Therefore, it is important to remove tramp oil from coolant formulations promptly and completely to minimize these adverse effects. Prompt and efficient separation of tramp oil from coolant also extends coolant life, improves machining, and minimizes maintenance. It is also important to separate tramp oil from wash water to minimize the amount of water which must be used, and thereby save storage and disposal costs.
A number of skimmers have been developed to separate oil and water mixtures, but most of these are expensive, inefficient or require a large amount of floor space. Previously available skimmers are also difficult to adjust and keep properly adjusted for efficient removal of the separated products for a variety of operating temperatures and materials.